Oilless air motor assembly for hydraulic pumps

Abstract

An oilless air motor assembly and method useable for driving hydraulic pumps and the like. The air motor assembly comprises a slide valve that moved back and forth relative to a valve sleeve situated about the slide valve. A low friction or lubricious dry seal member is disposed between the slide valve and the valve sleeve, thereby eliminating the need for added oil or lubricant and additionally avoiding the need for precise machining and matching (e.g., honing and lapping) of the slide valve and valve sleeve. Also provided is a kit for converting a previously manufactured air motor assembly that requires oil or added lubricant to an oilless air motor assembly. Such kit comprises the slide valve, valve sleeve and dry seal member as well as other optional parts associated with those elements.

1. An air piston actuating valve assembly kit for converting an oiled air motor apparatus that requires added lubricant to a dry air motor apparatus that does not require lubricant; wherein the oiled air motor apparatus comprises a body having a bore; an air cylinder that extends from said body and opens to said bore; a first manifold, a second manifold, a third manifold, an air inlet port that leads to the first manifold, an air exhaust port that leads to the second manifold, and at least one passageway that leads from the third manifold and opens into the upper end of the air cylinder, an air piston assembly comprising i) an air piston in said cylinder provided with a hollow stem operative in the body bore and having ports opening through the bottom thereof and ii) a slide valve and valve sleeve disposed in the bore about the air piston, said slide valve sleeve providing communication between the air inlet and the body bore and between the air exhaust and the upper portion of the air cylinder via the passageway when said slide valve is in one of said positions and between the air inlet and the upper end of the air cylinder via the passageway and between the body bore and the air exhaust when the slide valve is in the other of said positions; said air motor apparatus further comprising a pilot valve disposed within the slide valve, the pilot valve having an axial bore with a piston at one end, said pilot valve being shiftable by air pressure from the inlet entering the body bore, as controlled by the slide valve; said oiled air motor apparatus further comprising a first check valve carried by the pilot valve to allow air to be receive through the port of the air piston; a second check valve carried by the pilot valve to allow air to pass from beneath the air piston into the body bore, wherein the slide valve slides in metal to metal contact with the sleeve and lubrication is required between the slide valve and the sleeve when the slide valve slides in metal to metal contact with the sleeve and lubrication is required between the slide valve and the sleeve during normal operation of the air motor, and wherein the kit comprises:
 at least a replacement air piston actuating valve assembly comprising i) a replacement valve sleeve disposable in the bore about the air piston, said replacement slide valve being moveable between an upper position and a lower position, said replacement slide valve providing communication between the air inlet and the body bore and between the air exhaust and the upper portion of the air cylinder via the passageway when the slide valve is in one of said positions and between the air inlet and the upper end of the air cylinder via the passageway and between the body bore and the air exhaust when the sleeve valve is in the other said positions and ii) a dry seal member disposable between the replacement slide valve and the replacement valve sleeve, said dry seal member being formed of lubricious material that eliminates the need for added lubricant during routine operation of the air motor apparatus. 
 
   
   
     2. A kit according to  claim 1  further comprising a dry seal retaining apparatus which prevents the seal member from migrating upwardly on the replacement piston. 
   
   
     3. A kit according to  claim 2  wherein the dry seal retaining apparatus comprises a retaining ring seating groove formed in the air piston and a dry seal retaining ring, the retaining ring being positioned above the dry seal member and seated within the retaining ring sealing groove such that the dry seal member and retaining ring are prevented from migrating upwardly above the retaining ring seating groove. 
   
   
     4. A kit according to  claim 1  wherein the dry seal member has an inner surface and an annular o-ring seating grove formed in said inner surface, and wherein the kit further comprises an o-ring that is sized to be seated in the o-ring seating groove and captured between the inner surface of the dry seal member and slide valve. 
   
   
     5. A kit according to  claim 1  wherein the dry seal member has an inner surface and an annular o-ring seating grove formed in said inner surface, and wherein the kit further comprises:
 a dry seal retaining apparatus which prevents the seal member from migrating upwardly on the replacement piston; and, 
 an o-ring sized to be seated in the o-ring seating groove and captured between the inner surface of the dry seal member and slide valve. 
 
   
   
     6. A kit according to  claim 1  wherein the dry seal member is formed at feast partially of lubricious material that comprises a polymer. 
   
   
     7. A kit according to  claim 6  wherein the lubricious material comprises polytetrofluoroethylene. 
   
   
     8. A kit according to  claim 6  wherein the lubricious material comprises a graphite filled polymer. 
   
   
     9. A kit according to  claim 8  wherein the graphite filled polymer comprises graphite filled polytetrofluorothylene. 
   
   
     10. A kit according to  claim 9  wherein the graphite filled polytetrafluoroethylene contains approximately 25% by weight graphite.